This disclosure relates to flow field plates in a fuel cell. Fuel cells typically include an anode catalyst, a cathode catalyst, and an electrolyte between the anode and cathode catalysts for generating an electric current in a known electrochemical reaction between reactants, such as fuel and oxidant. The fuel cell may include flow field plates with channels for directing the reactants to the respective catalyst. Conventional fuel cells utilize inlet and exit manifolds that extend through the flow field plates to deliver the reactant gases and coolant to the channels and receive exhaust gas and coolant from the channels. The flow field plates are typically rectangular.
The locations of the manifolds often necessitate a multi-pass flow field design in which a reactant flows from one side of the flow field to the other through a first set of channels and turns to flow back across the flow field in another set of channels to make at least several passes over the flow field. One challenge associated with a multi-pass design is achieving high fuel cell performance. For instance, the humidity, temperature, and other properties of the reactant gases change significantly through the channels and can diminish the performance of the fuel cell. Single pass designs with specific arrangements among the fuel, air, and coolant streams have been proposed as a solution to reduce the effects of changes in the humidity and temperature of the gases, for example. However, single pass designs do not provide adequate distribution of the reactant gases to the catalyst to achieve the desired performance with the given packaging and manifold location constraints.